Conventional magnetic disk drives are information storage devices which utilize at least one rotatable magnetic media disk with concentric data tracks, a read/write transducer for reading the data from or writing the data to the various tracks, an air bearing slider for holding the transducer adjacent to the track generally in a flying mode above the media, a suspension for resiliently holding the slider and the transducer over the data tracks, and a positioning actuator connected to the transducer/suspension combination for moving the transducer across the media to the desired data track and maintaining the transducer over the data track during a read or a write operation.
The suspension is required to maintain the transducer and the slider adjacent to the data surface of the disk with a low controlled loading force. The actuator positions the transducer over the correct track according to the data desired on a read operation or to the correct track for placement of the data during a write operation. The actuator positions the transducer over the correct track by shifting the transducer/suspension combination generally transverse to the track.
The air bearing slider supports the transducer above the disk with a cushion of air that is generated by the rotating disk. Because the recording density of a magnetic disk drive is limited by the height of this air cushion between the transducer and the media, a goal of air bearing slider design is to "fly" the slider as close as possible to the magnetic media while avoiding physical impact with the media.
Alternatively, the transducer may operate in contact with the disk. Touching the media presents unique problems in wear and, during operation of the disk file, the possibility of a catastrophic impact between the transducer and an asperity on the media. To minimize these problems, it has been recognized that the loading force on the suspension system must be reduced to a low level. A variety of mechanisms have been disclosed which attempt to implement such a contact recording disk file. Structured to work in a perpendicular recording environment, these devices permit the head and suspension to be easily manufactured. U.S. Pat. Nos. 5,041,932; 5,073,242; and 5,111,351 entitled "Integrated Magnetic Read/Write Head/Flexure/Conductor Structure" granted to Harold J. Hamilton disclose an integral magnetic transducer/suspension structure having the form of an elongated dielectric flexure or suspension body with a magnetic read/write transducer embedded at one end. Integral transducer/suspension assemblies of this general form are sometimes referred to as "reed" devices because of their rough similarity in shape to a reed for a musical instrument. In a preferred embodiment, Hamilton discloses an elongated, dielectric flexure body of aluminum oxide having a magnetic pole structure and helical coil integrally formed at one end of the flexure body with embedded copper conductor leads running the length of the flexure body to provide electrical connection for the transducer. The integral structure is fabricated utilizing conventional vapor deposition and photolithography techniques.
As noted above, contact recording permits higher recording densities unaffected by variations in flying height. The rate at which such recorded data can be read from or written to the magnetic recording device is inherently limited by the rate at which the magnetic media spins. Higher rotation rates are desirable since they result in faster access to data. Unfortunately, high spin rates in combination with the low static load of a contact recording transducer/suspension assembly can cause the transducer to lose contact with the magnetic media. This phenomena is known as "lift-off" of the transducer from the media. The linear speed at which the lift-off occurs is known as the lift-off velocity. For a given disk rotation rate, the lift-off problem is more severe at the outer radius of the disk where the highest relative linear velocity between the media and the transducer is experienced.
This lift-off problem is typically addressed by increasing the static load on the suspension assembly and thereby increasing the force that maintains the transducer in contact with the media. This solution has the undesirable effect of increasing the wear caused by the sliding contact of the transducer and the disk surface. High wear rates limit the useful life of the magnetic disk drive and, if high enough, may render the device impractical. Furthermore, increased suspension loading increases the likelihood that contact with a disk asperity will damage the transducer/suspension assembly. In addition, increased static load on the suspension increases the stiction force between the transducer and the media at zero velocity. Overcoming this force during the start of disk rotation can damage the disk and the transducer/suspension assembly. For the foregoing reasons, there is a need for an apparatus that addresses the lift-off problem created at high rotation rates without increasing the suspension loading force.